Gas turbine engines include a compressor, combustor and turbine in flow series along a common shaft. Compressed air from the compressor is mixed with fuel in the combustor to generate hot combustion gases that rotate the turbine blades and drive the compressor. Improvements in the thrust and efficiency of gas turbine engines are linked to increasing turbine entry temperatures, which places a heavy burden on turbine blades. Consequently, there is significant interest in developing improved cooling techniques for airfoils in gas turbine engines.